CD4 and infection: Nevertheless, CXCR6 was highly expressed in CD4+ TIA cells from memory mice but also in NKG2D+CD4+CD44+ T cells from control mice, which could be stimulated to produce IFN-γ in vitro, but were not recruited to the site of infection in vivo (SI Appendix, Figs. S2 D and E and S4L), hinting toward alternative recruitment mechanisms.